The present invention generally relates to the field of fasteners such as rivets and the like, and more particularly to a self-polishing and tapping rivet assembly.
Blind setting rivets are typically used to fasten sheet metal work pieces or the like together when access is available to only one side of the work pieces. However, application of blind setting rivets may at times be cumbersome. For example, in many applications, special jigs must be used to maintain exact alignment of the work pieces from the time the hole is drilled until the rivet can be applied.
Because of these and other limitations, self-drilling blind setting rivets were developed. These rivets employ specialized drill heads which may be difficult to manufacture and are thus prohibitively expensive for many applications. Further, such rivets may leave a burr on the outer layer of the work piece materials. This burr may prevent proper seating of the rivet and may cause fractures in work pieces as it is applied, resulting in a weak joint. Known to the art are self-drilling rivets having deburring ears to remove burrs during the drilling operation. However, the drill bit of such rivets removes work piece material to create a hole for the rivet shank. This removed material may fall within an enclosed area creating a possible nuisance or hazard.
Typical drills have spirals designed to help the metal edges cut and spiral the shrapnel out. In a typical self-drilling rivet the spirals are designed to help the cut metal edges to create shrapnel which requires that high torque be placed on the mandrel of the rivet assembly.
U.S. Pat. No. 5,915,901 describes the use of the excurvations formed during application to increase application strength. However, in some applications, a polished aperture is desirable. Consequently, it would be advantageous to provide a blind setting rivet that would be both self-tapping and self-polishing instead of only self drilling (using a drill bit) or only self-tapping (using a screw tip). Such a self-tapping, self-polishing rivet would remove all excurvations that would leave a clean aperture. Additionally, a self-tapping and self-polishing rivet would be less expensive and easier to manufacture than the self-drilling rivets (using a drill bit) and would require less torque during application.
Accordingly, the present invention is directed to a self-tapping and self-polishing blind setting rivet assembly capable of permanently fastening one or more work pieces or the like together and/or to another object. In one embodiment, the rivet assembly may further include a hollow cylindrical threaded bolt head onto which a nut may be affixed to provide a means to removably attach other work pieces, components or the like.
In exemplary embodiments of the invention, the self-tapping and self-polishing blind setting rivet assembly comprises a rivet body having a hollow tubular sleeve and an enlarged flattened head. The rivet body surrounds a mandrel having a weakened area of reduced diameter to allow detachment of the mandrel shaft following application of sufficient axial force to the shank. This application of force sets the rivet by causing a tapered shoulder section of the mandrel to deform the rivet sleeve. The mandrel shank is terminated in a self-tapping and self-polishing auger that punctures, spreads, self-taps and self-polishes an aperture in the work piece(s) through which the rivet sleeve passes. The self-tapping and self-polishing auger includes a generally longitudinally formed groove providing one or more cutting edges that incrementally shave or carve small amounts of work piece material allowing torque to be dispersed over several small cutting edges simultaneously.
It is to be understood that both the forgoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the general description, serve to explain the principles of the invention.